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AERODINAMIC ANALISYS OF DOUBLE-WINGLET WITH VARIOUS DOWNWARD

WINGLET ANGLE USING CFD Agus Suandi, Helmizar and Vihartiyah Aisyah

University of Bengkulu, Bengkulu, Indonesia agus_suandi@unib.ac.id

Abstract The winglet on an aircraft wing aims to reduce the occurrence of vortex on the

wingtip so as to improve the aerodynamic performance of the aircraft. Winglet increase the effectiveness of the wing aspect ratio which reduces drag and also increases lift so as to reduce aircraft energy consumption. In this study wingtip modifications were carried out using double-winglets on the NACA 65(3)-218 airfoil wings with the upward winglet angle constant 45o and various downward winglet angles 30o, 45o, 60o, and 90o tested at various angles of attack (AoA) .The objectives of the analysis were to compare the aerodynamic characteristics and to investigate the performance of airplane wing without winglet, blended winglet and double winglet. The CFD simulations were performed at low subsonic flow speed in ANSYS CFD solver. Spalart-Allmaras turbulence model and 3-dimensional tetrahedrons mesh were used to compute the flow around the model. The aerodynamic characteristics of lift coefficient (CL), drag coefficient (CD) and lift-to-drag coefficient ratio (CL/CD) were compared and it was found that characteristic aerodynamic double-winglet with various downward winglet angle increase CL value and decrease CD value with the result CL/CD ratio go up. The optimum double-winglet occurs in downward winglet angle 60º because it increasing CL/CD ratio value 87.56% compare to wing without winglet and 8.41% compare to blended winglet.

Keywords: Aerodynamics, CFD, Multi Winglet, Aircraft

1 Introduction In terms of minimizing vortex on me the aircraft can be done by modifying the wing of the aircraft

on the wingtip by giving a winglet (Jodha, 2017). Winglets are part of an aircraft that are located on a wingtip. Winglets can increase fuel efficiency and reduce the value of induced drag so that it can

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increase aircraft mileage (Jodha, 2017). Induced drag is a drag caused by the vortex phenomenon that forms behind the wings of an aircraft wingtip (Anderson, 1997). There are several types of winglets, one of which is blended winglet. Blended winglet is a wingtip that is bent towards the wing. Several studies to improve winglet performance have been conducted such as (Beechook & Wang, 2013) (Helal et al., 2016), (Myilsamy D & Thirumalai Y, 2015), (Samil et al., 2018), (Munshi et al., 2018) and many others.

Research on the NACA 65 (3) -218 airfoil states that winglets still do not provide optimal aircraft performance at different flight phases. But it was found that winglets with a 45º cant angle have the highest CL/CD ratio at each angle of attack, especially at 4º angle of attack (Beechook & Wang, 2013). Research also carried out on the NACA 65 (3) -218 airfoil for winglets with a 90º cant angle has a relatively greater CL/CD ratio at a 4º angle of attack (Helal et al., 2016). Research on the NACA 4412 airfoil using AcuSolve® software for winglets with a cant angle of 90º has a max CL/CD ratio value at an attack angle of 2º of 11.18 (Myilsamy D & Thirumalai Y, 2015). Comparing the results of the research on the other NACA 4412 airfoil using ANSYS Fluent software for winglets with a cant angle of 60º has a CL/CD ratio value of max at an attack angle of 5º (Samil et al., 2018).

In the results of previous studies on blended winglets, the wingtip modification using double-winglets on the NACA 65 (3) -218 airfoil wing winglets was kept constant with 45o and various downward winglet angles of 30o, 45o, 60o, and 90o. tested at the angle of attack 0o, 4o, 8o and 12o to determine the effect on aerodynamic characteristics in the form of lift coefficient, drag coefficient and lift to drag coefficient ratio. From this study, quantitative data will be obtained in the form of aerodynamic characteristics on NACA 65 (3)-218 airfoil wings without winglets, blended winglets and double-winglets to analyze the effect of the double-winglet on the aerodynamic characteristics of the NACA 65 (3)-218 airfoil wing.

2 Process Methodology

2.1 Validating Procedure A similar numerical model rectangular wing without winglet and blended winglet at a cant angle

45°has been adopted. Wing and winglet cross sections are NACA 65(3)-218 airfoil section. Numerical models similar to mesh size and type have been developed for wings without winglets

and blended winglets 45o to verify numerical models with experimental data and numerical models from the literature. Measurements werw used to verify the work that has been made. This work refers to the results obtained from (Beechook & Wang, 2013). Present work data retrieval uses Ansys Fluent, whereas the referred data was taken using Ansys CFX.

Based on the results that were believed to be good, with the same method carried out further simulations to determine the aerodynamic characteristics of the double winglets with upward winglet angle 45o and downward winglet angle variations.

2.2 Modelling The shape of the NACA 65(3)-218 airfoils formed from these coordinates can be seen in Figure 1.

Figure 1. NACA 65(3)-218 Airfoil Section

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The aircraft wing and winglet modeling was carried out with NACA 65(3)-218 airfoil used ANSYS DesignModeler software. Modeling create base on airfoil NACA 65(3)-218 2D coordinate geometry. Configuration and dimension of wing, blended winglet, and double winglet model for NACA 65(3)-218 airfoil shown Figure 2 and Table 1.

Figure 2. Model Dimension

The specifications of the dimensions of the simulation model are described below.

Table 1. Winglet Dimensions

(a) Wing without winglet (b) Chord wing root

(c) Blended winglet cant 45o (d) Chord winglet up tip

(e) Double winglet downward angle 60º (f) Tip chord up and downward winglet

Parameter Dimension Chord wing root (c) : 0.12 m Wing Span (S) : 0.33 m Upward and Downward Chord Winglet Tip (c1) : 0.06 m Winglet span (S1) : 0.05 m Up Winglet angle (contant) : 45º Downward winglet angle variant : 30º,45º,60º and 90º

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Wing model was made in the form of wing without winglet, blended winglet and double-winglets. Blended winglet use a fixed bend angle (cant) of 45º compared to double-winglets varying only on downward winglet namely 30º, 45º, 60º, and 90º. The simulation model can be seen in Figure 3.

Figure 3. Rectangular Wing Model, (a) Wing; (b) Blended Winglet; (c) Double-Winglet

2.3 Meshing and Pre-Processing The process of meshing is the process of dividing a solid model into small elements that serve as

an area for calculation and iteration of a simulation. This stage had been carried out in Ansys Meshing software. This process was to facilitate the software in making calculations so that the results of the analysis can approach the actual results. The meshing result is shown in Figure 4.

Figure 4. Meshing

The meshing data input used can be seen in Table 2.

Table 2. Mesh details

The number of nodes and elements used in each wing without winglet, blended winglet and double winglet to be the case for a grid with around 2250000 cells to 2450000 cells.

(a)

(b)

(c)

No. Input Set 1 Advanced Size Function Curvature 2 Relevance Center Fine 3 Smoothing Medium 4 Method Tetrahedrons

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2.4 Boundary Conditions Determination of boundary conditions in the model that must be defined and given several

parameters so that the iteration process can run according to the desired conditions. These boundary conditions were required at all boundary, namely inlet, outlet and the walls as shown in Figure 5.

Figure 5. Boundary Conditions

This stage includes determining model and boundary conditions, the properties of material and fluid used. Boundary conditions used can be seen in Table 3. Data retrieved were drag coefficient (CD) and lift coefficient (CL) on wing without winglet and blended winglet NACA 65(3)-218 with cant angle 45º.

Table 3. Boundary Condition

3 Result and Discussions The analysis was done for further simulation cases. Based on data experiment and CFD simulation

(Beechook & Wang, 2013), It has been continued to analyze double winglets with different downward winglet angle for NACA 65(3)-218 airfoil.

No Input Set

1 Velocity Subsonic (35m/s)

2 Temperature 288.2 K

3 Solver Pressure-based

4 Turbulence Model Spalart -Allmaras model

5 Atmosphere pressure 101000 Pa

6 Air Density 1.225 kg/m3

7 Angle of attack 0º, 4º, 8º and 12º

Inlet

Inlet

Inlet

Inlet

Outlet

Symmetry

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Figure 6 shows that wing without winglets have greater drag coefficient (CD) values compared to various winglets.

Figure 6. Drag coefficient (CD) Comparison between Wing without Winglet, Blended Winglet and Double

Winglet with Various Downward Winglet Angle Configurations, Versus Angle of Attack (α).

It can be stated that various winglets have good resistance to air compared to wing without winglets. Blended winglets with cant angle 45º have a slightly higher coefficient of drag compared to various double-winglets. As for various double-winglets with a cant angle 60º, it has a smaller drag coefficient (CD) compared to other various double-winglets. So quantitatively, a double-winglet with a cant angle 60º has the best resistance to air.

A graph of the comparison of lift coefficient (CL) values with various AoA shown in Figure 7.

Figure 7. Lift Coefficient (CL) Comparison between Wing without Winglet, Blended Winglet and Double

Winglet with Various Downward Winglet Angle Configurations, Versus Angle of Attack (α).

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

-2 0 2 4 6 8 10 12 14

Dra

g C

oeffi

cien

t (C

D)

Angle of Attack(º)

Without WingletBlended Winglet Cant 45ºDouble-Winglet Downward angle 30ºDouble-Winglet Downward angle 45ºDouble-Winglet Downward angle 60ºDouble-Winglet Downward angle 90º

0.00

0.20

0.40

0.60

0.80

1.00

-2 0 2 4 6 8 10 12 14

Lift

Coe

ffici

ent (

CL)

Angle of Attack (º)

Without WingletBlended Winglet Cant 45ºDouble-Winglet Downward angle30ºDouble-Winglet Downward angle 45ºDouble-Winglet Downward angle 60ºDouble-Winglet Downward angle 90º

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Figure 7 shows that wing without winglets have smaller lift coefficient (CL) values compared to other winglets. Blended winglets with cant angle 45º have lift coefficient values that are slightly lower compared to various double-winglets. As for various double-winglets with cant angle 30º, they have higher lift coefficient (CL) compared to other various double-winglets. The double-winglet with downward winglet 30º for the 0º angle of attack has the highest lift coefficient (CL), so that during the cruise it is able to carry heavier loads compared to the others. For CL max value on double-winglet with downward winglet angle 30º higher than the others which is 0.96 at AoA 12o, this shows that double-winglet with cant angle 30º has better take-off performance also. So quantitatively, a double-winglet with a cant angle of 30º during a cruise is able to carry heavier loads and has a better take-off performance compared to other various wings.

Graph comparison of CL/CD ratio with various angles of attack can be seen in Figure 8.

Figure 8. Lift-to-Drag Coefficient Ratio (CL/CD) Comparison Between Wing Without Winglet, Blended

Winglet and Double Winglet with Various Downward Angle Configurations, Versus Angle of Attack (α).

Figure 8 show that wing without winglet has the smallest CL/CD ratio compared to various winglets. Blended winglets with cant angle 45º have lower CL/CD ratio values compared to various double-winglets. As for various double-winglets, the CL/CD ratio is high. On the graph the minimum CL/CD ratio value for each wing is at 0º attack angle with the highest CL/CD ratio value occurring in the double winglet with cant angle 30º which is 6.27. If the CL/CD max value on each wing is at an AoA of 4º with the most optimal CL/CD ratio value occurs in the double winglet with downward winglet angle 60º that is equal to 14.2. This indicates that the CL value obtained was quite high with a small CD value compared to various other wings.

4 Conclusion Analysis of the aerodynamics effect of double-winglet on aircraft wing with various cant angles

downward winglets using the CFD method on the NACA 65(3)-218 airfoil wingtip can increase the CL value and reduce the CD value so that the CL/CD ratio increases. The most optimal double-winglet occurs at the downward winglet angle 60º because it has a CL/CD ratio max at an angle of attack of 4º by increasing the CL/CD ratio by 87.56% of the wing without winglet and 8.41% of the blended winglet.

0

2

4

6

8

10

12

14

16

-2 0 2 4 6 8 10 12 14

Rat

io C

L/C

D

Angle of Attack (º)

Without WingletBlended Winglet Cant 45ºDouble-Winglet Downward angle 30ºDouble-Winglet Downward angle 45ºDouble-Winglet Downward angle 60ºDouble-Winglet Downward angle 90º

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References

Anderson JD. (1997). A History of Aerdynamics. Rycroft MJ, Stengel RF, editor. New York: United States of America by Cambridge University Press. (pp. 73).

Beechook A, Wang J. (2013). Aerodynamic Analysis of Variable Cant Angle Winglets for Improved Aircraft Performance. In: Proceedings of the 19th International Conference on Automation and Computing. London,UK: Brunel University.

Coiro DP, Nicolosi F, Scherillo F, Maisto U. (2008) Design of Multiple Winglets to Improve Turning and Soaring Characteristics of Angelo D’Arrigo’s Hang-Glider : Numerical and Experimental Investigation. 87(1):74–85.

Helal HSM, Khalil EE, Abdellatif OE, Elhariry GM. (2016). Aerodynamic Analyses of Aircraft-Blended Winglet Performance. J Mech Civ Eng. 13(3):65–72.

Houghton EL, Carpenter PW, Collicott SH, Daniel T V. (2013). Aerodynamics for Engineering Students. Sixth Edit. Vol. 53, Butterworth-Heinemann. Elsevier.

Jodha P. (2017). Aircrafts winglets analysis in CFD. England. Munshi A, Sulaeman E, Omar N, Ali MY. (2018). CFD Analysis on the Effect of Winglet Cant

Angle on Aerodynamics of ONERA M6 Wing. J Adv Res Fluid Mech Therm Sci 45. (1):44–54. Myilsamy D, Thirumalai Y, P.S P. (2015). Performance Investigation of an Aircraft Wing at

Various Cant Angles of Winglets using CFD Simulation. In: Altair Technology Conference. India: Altair Technology Conference. (pp. 1–23).

Samil PC., Sanjid M, Mohammed EA, Krishnan A, Jacob T., (2018). Performance Analysis of Winglet using CFD. Int Res J Eng Technol. 05(04):4154–9.

Smith MJ, Komerath N, R.Ames, O.Wong. (2001, June). Performance Analysis of a Wing With Multiple Winglets. American Institute of Aeronautics and Astronautics. AIAA-2001-2407.

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